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題名 | 低壓化學氣相沉積氧化鋅奈米線光電特性及成長機制之探討=An Investigation on the Opto-Electronic Properties and Growth Mechanism of LPCVD ZnO Nanowires |
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作者 | 張宇能; 李于豪; Chang, Yu-neng; Lee, Yu-how; |
期刊 | 龍華科技大學學報 |
出版日期 | 20070300 |
卷期 | 22 2007.03[民96.03] |
頁次 | 頁47-58 |
分類號 | 440.34 |
語文 | chi |
關鍵詞 | 氧化鋅; 奈米線; 低壓化學氣相沉積; ZnO; Nanowire; LPCVD; |
中文摘要 | 本研究使用低壓化學氣相沉積(LPCVD)法成長氧化鋅奈米線,採用Zn(C[904e]H[8e66]O₂)₂為先驅物,實驗分兩梯次,首先使用水平式熱牆化學氣相沈積系統,可成長成奈米柱,經由使用參雜技術與用銅網為基材可有效的讓奈米柱變細,但成果未盡理想。後來採用垂直式冷牆化學氣相沈積設備,在過渡金屬緩衝層和電漿表面前處理輔助下,達到較佳的奈米線成長。經XRD,SEM,及PL分析結構及光電特性指出在氧氣流量90sccm,氬氣流量60sccm,沉積壓力210torr,蒸發溫度140℃,沉積溫度600℃,沉積時間1hr下,可長出線徑約20nm的奈米線其PL僅有380nm之near band edge峰,成果接近國際水準。 |
英文摘要 | Due to the quantum confinement effect, zinc oxide nanowires have the potential applications in filed emission display, micro-array sensors, quantum transistor, and computer. In this study, by using sputtered metal seed layers pre-coated substrates and plasma surface treatment, we have developed a low pressure metal organic chemical vapor deposition (LP-MOCVD) process to deposit optic quality ZnO nanowires. The first stage of research was performed n a hot wall horizontal LPCVD reactor, using zinc acetylacetonate (Zn(acac) ₂) as precursor, at 60-200 torrs, with deposition temperature from 500 to 700°C. XRD and FESEM studies show that the ZnO nanostructure was influenced primarily by the deposition temperature, composition and microstructure of surface. For LPCVD from 550 to 600°C, one dimensional ZnO nanocoulmns and nanorods with diameter less than 100 nm were observed. PL spectra show single excitonic related peak at 380 nm, implying satisfactory quality for ZnO lattice in these wires. Experimental data proved that copper was the most efficient catalyst to promote ZnO nanowire growth. FESEM images suggest that this filamentary growth might be driven by a vapor-liquid-solid (VLS) mechanism. The second stage of research was conducted by using a cold wall vertical CVD reactor, which offer a better gas intermixing effect and eventually reduction on the diameter of ZnO nanowires. ZnO nanowires with average diameter less than 50 nm, and a sharp PL 380 nm peak were obtained, from LPCVD at 210 torr, and 600°C. However, the Pl peak width increases as the average diameter decreases. According to SEM, film growth mode is assigned to island or Volmer-Weber mode, XRD studies show that film growth was influenced by composition and structure of substrate surface, at 550°C. For LPCVD above 600°C, (002) becomes the preferential orientation in most ZnO layers. XRD data also show that at 700°C, (002) peak intensity decreases. FESEM results show, for ZnO LPACVD at 500-700°C, with oxygen concentration at 50-90%, continuous but rough films form. FESEM shows surface morphology depends on buffer layer at temperature from 500 to 550°C. PL results show that, for LPCVD on some RF sputtered buffer, at 550-600°C, 60-100 torr, and oxygen concentration of 90%, ZnO deposits exhibit a sharp Pl spectral line at 380 nm, without tailing or green emission. Such facts reflect a pure ZnO band structure, with a bandgap of 3.2 eV, and non detectable deep level emissions. |
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